In a typical two-way radio communication system, fixed stations are geographically dispersed to provide communication support for mobile radios. A mobile radio communicates directly with a fixed station which routes such communications to another fixed station or mobile radio. Generally, the fixed stations and mobile radios exchange information in order to properly manage the resources used for communication. For example, a mobile radio may exchange call setup information with a fixed station, including channel and timing information, in order to service a particular call.
Mobile radios are often battery-powered devices, and much effort has been expended in order to minimize power consumption and to prolong battery life in these devices. In this endeavor, power control techniques have been employed in which information is exchanged between the mobile radio and the fixed station in order to determine the appropriate power level to be used in supporting a given communication session. In many prior art systems, power control information is conveyed on a control channel established for such purposes. For example, a time division multiple access (TDMA) communication system may have a time slot allocated for communicating control information. Similarly, a frequency division multiple access (FDMA) communication system may have a frequency channel devoted to such purposes.
A problem exists in systems that employed a simplex communication channel that is captured for the duration of a transmission session, when such session extends for an appreciable period of time. In such prior art systems, the mobile radio is busy supporting the transmission session, and is not in a position to receive control information until the transmission session is terminated. As a result, the mobile radio may have changed location or operating environment in such a way that the power level setting is no longer appropriate for that particular transmission session. Thus, the power level may be too low, thereby risking a loss of communication, or the power level may be too high, thereby wasting power and reducing battery life. Similarly, the conveyance of other control information may be delayed resulting in various problems.
It is desirable to frequently communicate control information between a mobile radio and a fixed station during a communication session to permit more precise management of device operating parameters and system resources. However, in some communication systems such as those that allow for uninterrupted transmission on a dedicated frequency channel, the receipt of important control information may be delayed with adverse consequences. Therefore, a new method for communicating control information is needed.